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New slats make the Golden Gate Bridge sound like a David Lynch movie

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Re: New slats make the Golden Gate Bridge sound like a David Lynch movie

#141

Post by johnfn »

closeparen wrote: post #93
johnfn wrote: post #59

Earlier quoted context omitted.

Pretty interesting hypothesis! I don't think so, though. It was a fairly electronic sounding boop, almost like a low sine wave. A fog horn sound has more acoustic qualities to it. Also, if it was a fog horn, I don't know why it would only be audible in Nob Hill and no where else I've been in SF.

The Bay foghorns are electronic tones; they don’t sound like classic/cartoon foghorns at all.

Wow. I went online and found an audio recording: https://www.youtube.com/watch?time_continue=12&v=CPUs2KnAyhU...

Yup, the tone at 0:08 is pretty much the exact tone I heard. Mind-blowing. Never would have imagined that's what a fog horn sounded like. I expected them to all be much deeper tones like the ones that come a few seconds later. I guess there must be weird acoustic qualities that make only the higher toned ones carry into Nob Hill.

Re: New slats make the Golden Gate Bridge sound like a David Lynch movie

#142

Post by AmericanChopper »

dessant wrote: post #14

I'm just glad they identified the source of the hum, many people are impacted for years by unexplainable sounds, and it is maddening. It took me and my neighbours a month to find the source of a hum that was resonating with our windows. It was torture, with midnight walks and lurking around potential sources, mapping nearby industrial sites, and questioning our sanity, while our windows were vibrating without a stop.…

I get woken up once a week by a sound similar to the one the Golden Gate Bridge is making. It starts around 4am, except it comes in short pulses. I recently figured out it was the breaks on the garbage truck that services my neighbourhood. They make a really loud high pitch hum every time it stops, and when the truck isn’t particularly close by, you can’t hear the rest of the truck sounds, but you can hear that hum very loudly.

The local council didn’t really care when I told them. It doesn’t bother me too much because I get up quite early anyhow, but I imagine this truck would manage to bother a rather large number of people every week. I wonder if the sound will go away next time it’s serviced.

Re: New slats make the Golden Gate Bridge sound like a David Lynch movie

#143

Post by close04 »

rasz wrote: post #70
dustym wrote: post #24

Earlier quoted context omitted.

Two unrelated anecdotes: 1. A few years ago I spent some time in Falmouth, MA and there was an ongoing battle over newly installed wind turbines. The humming sound was getting to people, including to the point where they were getting headaches. Some people heard it and others didn't. The locals were going to war with the initiative. This article reminded me of that and I checked in on the ordeal. Looks like they shut…

1 Modern CFD techniques enable almost silent blades. If a $10 computer fan can have special dimples/channels why cant wind turbines https://www.quietpc.com/nf-a12x25-5v https://cougargaming.com/us/products/cooling/cfd_red_led_fan... https://aerocool.io/us/product/silent-master-blue-20cm/

Well... size matters. The tip of a wind turbine blade moves much faster (~25m/s, up to 80m/s in the biggest ones) than the tip of a silent computer fan (~5-6m/s, up to ~10m/s in the faster ones). You can make the blades more silent but there's a limit to what you can do when your blades move that fast and are up to 75m long. And any solution that reduces efficiency is probably a no go for manufacturers and operators.

From your links you can see that a 140mm computer fan at 1000RPM is noisier than a 120mm fan at 1200RPM. Even if the motor is quieter at the lower RPM, increasing the blade size is more than able to compensate and make it overall noisier, even with dimples and owl-wing tricks.

And it's not only the decibels that are the issue necessarily but also the frequencies which can propagate quite far and by all accounts are pretty disturbing. That low frequency hum that the blades produce by simply displacing air while they move is not a problem with a computer fan's tiny blades. And turbines come in farms.

Re: New slats make the Golden Gate Bridge sound like a David Lynch movie

#144

Post by Animats »

There should be an app for this.

To get direction and location, you need acoustic samples from multiple widely-spaced locations, all synchronized. Human ears are not wide enough apart to directionalize low frequencies, but with a baseline of tens or hundreds of meters from separate cell phones, it's not hard. Run a correlator, line up the samples, compute the hyperbolas of constant time offset, (like GPS and LORAN) and find the target.

This needs an app with timing accurate to a millisecond or so. Can you get that from cell phones? The built-in clock synchronization isn't that good. The GPS receiver has more accurate time, but you may not be able to get at that.

Re: New slats make the Golden Gate Bridge sound like a David Lynch movie

#145

Post by jungletime »

rasz wrote: post #70
dustym wrote: post #24

Earlier quoted context omitted.

Two unrelated anecdotes: 1. A few years ago I spent some time in Falmouth, MA and there was an ongoing battle over newly installed wind turbines. The humming sound was getting to people, including to the point where they were getting headaches. Some people heard it and others didn't. The locals were going to war with the initiative. This article reminded me of that and I checked in on the ordeal. Looks like they shut…

1 Modern CFD techniques enable almost silent blades. If a $10 computer fan can have special dimples/channels why cant wind turbines https://www.quietpc.com/nf-a12x25-5v https://cougargaming.com/us/products/cooling/cfd_red_led_fan... https://aerocool.io/us/product/silent-master-blue-20cm/

Experiment! How Does An Owl Fly So Silently?

https://www.youtube.com/watch?v=d_FEaFgJyfA

Re: New slats make the Golden Gate Bridge sound like a David Lynch movie

#146

Post by allannienhuis »

forgotmyp77 wrote: post #67
yread wrote: post #64

Earlier quoted context omitted.

Your description reminded me of a similar sound on my first night on anchor with my first chartered yacht. Turns out it was a fan in our inverter that was somehow switched on and it completely drained both our batteries (wrong installation) overnight so we couldn't lift the anchor nor start the engine in the morning

how did you get out of that one?

I've had this happen. Our boat has a separate battery for the generator, so normally if you accidentally drain the main and engine batteries, you can recharge via the generator. But during maintenance someone reset a switch that connected the generator battery to the mains without realizing it. We were in the proverbial middle of no-where - I had a 1+ hour row in my dingy to a remote camp to find someone to rescue us (jump-start the generator).

Now I never leave the dock without one of those portable car-starting batteries, completely disconnected from everything.

Re: New slats make the Golden Gate Bridge sound like a David Lynch movie

#148

Post by pointer_pointer »

johnghanks wrote: post #133
tobinfricke wrote: post #125

I tried making a spectrogram: https://twitter.com/nibot/status/1269347206445756416 I tried using baudline[1] (a 20-year-old program!) but it didn't work out-of-the-box on my current Linux installation. Instead I found something called Sonic Visualizer[2], which, while not real-time, worked out of the box. Using Pulse Audio 'pavucontrol' it was easy to configure Sonic Visualizer to use as its input the 'monitor' chann…

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please leave this site

Re: New slats make the Golden Gate Bridge sound like a David Lynch movie

#150

Post by gpm »

Animats wrote: post #144

There should be an app for this. To get direction and location, you need acoustic samples from multiple widely-spaced locations, all synchronized. Human ears are not wide enough apart to directionalize low frequencies, but with a baseline of tens or hundreds of meters from separate cell phones, it's not hard. Run a correlator, line up the samples, compute the hyperbolas of constant time offset, (like GPS and LORAN) a…

Sound travels, what, 30 centimeters a ms?

Bluetooth/wifi is good for at least a few meters, and should have latency of around a ms. Should be pretty easy to synchronize via that.

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